1. Field of the Invention
This invention relates to truck frames for use in rail vehicles having high torsional flexibility comprising a pair of longitudinal beams joined by crossbeams wherein the crossbeams' upper chords are welded to the lower chords of the longitudinal beams, the truck frame having middle crossbeams joining the parallel running longitudinal beams between the end crossbeams.
2. Discussion of Prior Art
It is known that truck frames of high torsional flexibility are used in rail vehicles. These highly flexible trucks have the advantage that the primary spring between the wheel axle bearing and the truck frame can be relatively stiff, and under certain circumstances can be entirely dispensed with. In a highly flexible truck, if the points of contact of the wheels with the rails are in a horizontal plane, the wheel loading will be equal at all points. Even if one point is not in this plane, as is the case, for example, in ramps leading up to superelevations in the rails, only very slight differences occur in the wheel loading, since the truck offers little resistance to such distortions. There is no danger, therefore, that a wheel might part from the rail.
These known truck frames of high torsional fiexibility were welded together from longitudinal and transverse beams of low resistance to torsion such that flexibility will not be impaired at the welds, it being necessary for that purpose that the longitudinal movements of the chords against one another, produced by the twisting of a beam, will not be restricted. In the known swivel truck frame, this is achieved by making the beams or at least their upper or lower chords offset. In particular, the longitudinal beams are offset downwardly, resulting in the possibility of making the ends of the longitudinal beams more torsion-resistant so as to prevent the ends from twisting in the event of a transverse force acting on the set of wheels. The crossbeams also are either offset as a whole, or at least their lower chords are curved to an arc which is able to absorb the shear movements, and the end is welded to the longitudinal beam. The truck frames are constructed in an H-like configuration, since due to the welding of crossbeams to the two face sides the torsional flexibility of the truck frame would be impaired.
Trucks of high torsional flexibility have proven to be very satisfactory. They are suitable for all kinds of rail equipment, namely passenger cars, short-haul cars and rail cars, streetcars and freight cars. They have very good dynamic characteristics and are suitable therefore even for high speeds. They can be made relatively light, and they make possible savings in the primary spring.
On account of these many different uses for trucks of high torsional flexibility, it has been necessary constantly to create new designs, because the requirements as regards the length and width of the truck frame, and its load carrying capacity, etc., vary greatly. The offset shape of the beams made it necessary every time to redesign the entire truck. Even a need to increase the distance between the wheel axles by 30 cm used to necessitate a large investment in a completely new design.
It is an object of this invention to provide a swivel truck frame which can be adapted to various requirements regarding dimensions, load carrying capacity and the arrangement of springs, brakes and, in some cases, motors and other additional equipment, without each time having to perform a complete new design with all of the detail drawings necessary for that purpose.